1. Field of the Invention
The present invention relates to a combination type thin film magnetic head having a writing inductive type thin film magnetic head and a reading thin film magnetic head including a magnetoresistive element, said heads being stacked on a substrate, and a manufacturing method thereof.
2. Explanation of the Related Art
Recently, a surface recording density of a hard disk drive has been improved, and the performance of a combination type thin film magnetic head has to be improved accordingly.
As a combination type thin film magnetic head, a head having an inductive type thin film magnetic head for writing and a magnetoresistive type thin film magnetic head for reading, which are stacked one on the other on a substrate, has been proposed and has been put to practical use. As a reading magnetoresistive element, in general, an element using a usual anisotropic magnetoresistive (AMR) effect, has been used so far, but an element using a giant magnetoresistive (GMR) effect, which has a larger resistance variation ratio than the AMR element by several times, has been developed.
In this specification, these AMR element and the GMR element or the like are referred to as a magnetoresistive type thin film magnetic head generically, or an MR element simply.
The surface recording density of several giga (G) bits per inch 2 can be realized by using the AMR element. Moreover, the surface recording density can be more improved by using the GMR element. In this way, the realization of a hard disk drive device in 10G byte or more becomes possible by raising the surface recording density.
One of factors for determining the performance of the reproducing head including such a magnetoresistive reproduction element is a height of the magnetoresistive reproduction element (MR height MRH). The MR height MRH is a distance of the magnetoresistive reproduction element whose edge is exposed to an air bearing surface measured from the air bearing surface. In the manufacturing process of the thin film magnetic head, desired MR height MRH is obtained by controlling an amount of polishing when the air bearing surface is polished.
On the other hand, in accordance with the improvement in the performance of the reproducing head, the performance of the recording head is required to be improved. It is necessary to raise the density of the truck on a magnetic recording medium in order to improve the surface recording density. For this purpose, it is necessary to make the width of a write gap on the air bearing surface narrow from several microns to the sub-micron order. The semiconductor processing technology is used to achieve this.
A throat height (TH) is one of the factors for deciding the performance of the writing thin film magnetic head. The throat height is a distance of a magnetic pole portion measured from the air bearing surface to an edge of an insulating layer by which a thin film coil is separated electrically, and it is desired to shorten this distance as much as possible. Reduction in size of the throat height TH is also decided by the polishing amount on the air bearing side.
Therefore, in order to improve the performance of the combination type thin film magnetic head including the stacked reading magnetoresistive type thin film magnetic head and writing inductive type thin film magnetic head, it is important to form the writing inductive type thin film magnetic head and the reading magnetoresistive type thin film magnetic head with well balancing.
FIGS. 1-9 show successive steps of manufacturing a conventional standard thin film magnetic head, in each figure, A is a cross sectional view of the entire thin film magnetic head, and B is a cross sectional view of the magnetic pole portion. Moreover, FIGS. 10-12 are a cross sectional of the entire conventional completed thin film magnetic head, a cross sectional view of the magnetic pole portion, and a plan view of the entire thin film magnetic head, respectively. In this embodiment, the thin film magnetic head is a combination type formed by stacking the readout inductive type thin film magnetic head and the reading MR reproduction element.
At first, as shown in the FIG. 1, an insulating layer 2 consisting of, for example, alumina (Al2O3) is deposited on a substrate 1 made of AlTiC in the thickness of about 5-10 xcexcm. Next, as shown in the FIG. 2, a first magnetic layer 3 constituting one magnetic shield protecting a MR reproduction element of a reproducing head from the influence of the external magnetic field is formed with the thickness of 3 xcexcm.
Then, as shown in the FIG. 3, after alumina is deposited by sputtering with the thickness of 100-150 nm, as an insulating layer 4, a magnetoresistive layer 5 made of a material having the magnetoresistive effect and constituting the MR reproduction element, is formed with the thickness of 10 nm or less, and then, is formed into a desired shape with a mask alignment of high accuracy.
Then, as shown in FIG. 4, again, an insulating layer 6 is formed, and the magnetoresistive layer 5 is embedded in the insulating layers 4 and 6.
Next, as shown in FIG. 5, a second magnetic layer 7 made of a permalloy is formed with the film thickness of 3 xcexcm. The second the magnetic layer 7 not only has a function as the other shield for magnetically shielding the MR reproduction element together with the above mentioned first magnetic layer 3, but also has the function as the one pole of writing thin film magnetic head.
Next, after a write gap layer 8 made of a non-magnetic material, for example, alumina, is formed with thickness of about 200 nm on the second magnetic layer 7, and then a magnetic layer made of a magnetic material having a high saturation magnetic flux density, for example permalloy (Ni: 50 wt %, Fe: 50 wt %) and nitride iron (FeN) is formed, and is shaped into a desired form with the mask alignment of high accuracy, thereby obtaining a pole chip 9. The truck width is defined by a width W of the pole chip 9. Therefore, it is necessary to narrow the width W of the pole chip 9 in order to achieve a high surface recording density.
In this case, a dummy pattern 9xe2x80x2 for connecting the second magnetic layer 7 with a third magnetic layer constituting the other pole, is formed at the same time. Then, after mechanical polishing or chemical mechanical polishing (CMP), a through-hole can be formed easily.
In order to prevent the effective write track width from being widened, that is, in order to prevent the magnetic flux from being widened at one pole during the data writing, the gap layer 8 in surroundings of pole chip 9 and the second magnetic layer 7 constituting the other pole are etched by the ion beam etching such as the ion milling. This state is shown in FIG. 5. This structure is called as a trim structure, and this portion becomes a magnetic pole portion of the second magnetic layer.
Next, as shown in FIG. 6, after forming an insulating layer 10 such as an alumina film having a thickness of about 3 xcexcm, the surface is flattened by for example CMP.
Afterwards, after an electrically insulating photoresist layer 11 is formed to a predetermined pattern by the mask alignment with high accuracy, a first layer thin film coil 12 of, for example, copper is formed on the photoresist layer 11.
Then, as shown in FIG. 7, after forming an insulating photoresist layer by the mask alignment with high accuracy on the thin film coil 12, the surface is flattened by baking at the temperature of, for example, 250-300xc2x0 C.
In addition, as shown in FIG. 8, a second layer thin film coil 14 is formed on the flattened surface of the photoresist layer 13. Next, after forming a photoresist layer on the thin film coil 12 by the mask alignment with high accuracy, the surface is flattened by baking at the temperature of, for example, 250xc2x0 C.
As described above, the reason for forming the photoresist layers 11, 13, and 15 by the mask alignment with high accuracy is to define the throat height TH and the MR height MRH by using the edge of the photoresist layer on the side of magnetic pole portion as a standard position.
Next, as shown in FIG. 9, a third magnetic layer 16 constituting the other pole is selectively formed with the thickness of 3 xcexcm on the pole chip 9 and photoresist layers 11, 13, and 15 by for example a permalloy according to the desired pattern.
The third magnetic layer 16 is contacted with the second magnetic layer 7 at a rear position away from the magnetic pole portion by means of the dummy pattern 9xe2x80x2, so that the thin film coils 12 and 14 pass through a closed magnetic path constituted by the second magnetic layer 7, the pole chip 9, and the third magnetic layer 16.
In addition, an overcoat layer 17 consisting of alumina is deposited on the exposed surface of the third magnetic layer 16.
Finally, the side surface on which the magnetoresistive layer 5 and the gap layer 8 are formed is polished to form the air bearing surface (ABS) 18 which is to be opposed to the magnetic recording medium.
The magnetoresistive layer 5 is also ground during the formation of the air bearing side surface 18, and thus an MR reproduction element 19 is obtained. In this way, the above mentioned throat height TH and MR height MRH are decided. The state thereof is shown in FIG. 10. In actual thin film magnetic head, pads for making electric connections to the thin film coils 12, 14, and MR reproduction element 19 are formed, but they are not shown. Moreover, FIG. 11 is a cross sectional view in which the magnetic pole portion of the combination type thin film magnetic head formed thus was cut by a plane parallel to the air bearing surface 18.
As shown in FIG. 10, an apex angle xcex8 between a segment S for connecting corner portions of side surfaces of the photoresist layers 11, 13, and 15 isolating the thin film coils 12 and 14 and the upper surface of the third magnetic layer 16, is also an important factor for determining the performance of the thin film magnetic head together with the above mentioned throat height TH and MR height.
Moreover, as shown in a plan view of FIG. 12, the width W of the pole chip 9 and the magnetic pole portion 20 of the third magnetic layer 16 becomes narrow and the width of the track recorded on the magnetic recording medium is decided by this width, so that it is necessary to narrow the width W as small as possible to achieve a high surface recording density. Moreover, in this FIG. 12, for the shake of simplify, the thin film coils 12 and 14 are shown by concentric circles.
Well, up to now, in the formation of the conventional thin film magnetic head, a particularly difficult problem after the formation of the thin film coils, is a miniaturization of the top pole formed along the coil projection, especially along its inclined portion (Apex) covered by the photoresist insulating layer.
That is, the given pattern is formed by depositing the photoresist with the thickness of 3-4 xcexcm after a magnetic material such as permalloy is plated to form the third magnetic layer on the coil projection having the height of about 7-10 xcexcm, and then the desired pattern is obtained by using the photolithography technology.
Here, if the thickness of 3 xcexcm or more is necessary for as the resist film patterned by the photoresist on the recessed portion of the mountain like coil, the photoresist of the thickness of about 8-10 xcexcm will be deposited at a root portion of the inclined portion.
On the other hand, in the third magnetic layer formed on the surface of the coil mountain portion which has such a height of about 10 xcexcm and on the flat write gap layer, a narrow track of the recording head is formed in the edge neighborhood in the photoresist insulating layer (for example, 11 and 13 in FIG. 7), so that the third magnetic layer have to make the patterning with the width of about 1 xcexcm. Therefore, the necessity for forming the pattern of width of 1 xcexcm is caused by using the photoresist film of the thickness of 8-10 xcexcm.
However, even if you form the narrow pattern with about 1 xcexcm width with a thick photoresist film such as 8-10 xcexcm, the crumble of the pattern etc. according to reflected light are generated during exposure due to photolithography and the decrease in the resolution happens due to the thick resist film, so that it is extremely difficult to pattern the narrow top pole used to form a narrow track, accurately.
Then, as shown in the above conventional embodiment, assuming that the data are written by the pole chip capable of forming the width of the narrow track recording head, it is proposed to improve the above problem by assuming the method for connecting the third magnetic layer to the pole chip after this pole chip is formed, in other words, by assuming structure divided into two, the pole chip deciding the width of the track and the third magnetic layer introducing the magnetic flux.
However, the following problems are still remained unsolved in the thin film magnetic head formed as described, especially in the recording head.
(1) The positional relationship of the pole chip 9 and magnetic layer 16 is decided by the alignment of photolithography, so that when viewing from the air bearing surface, there is a possibility that the central line of the pole chip and the central line of the third magnetic layer are shifted greatly, the leakage of magnetic flux might occur, and data might be written by the leakage flux from the third magnetic layer, an effective track width might be increased, and there is a problem of writing data on an adjacent track. It is necessary to widen the truck interval to avoid this problem, and thus the surface recording density will not be improved.
(2) The narrow pole chip 9 is brought into contact with the wide third magnetic layer 16 vertically and the magnetic flux is liable to be saturated at this portion, and therefore, the improvement of writing characteristic (Flux Rise Time) is not obtained satisfactory.
(3) The throat height TH and MR height MRH are decided based on the edge of the insulating layer isolating the thin film coil on the air bearing side, but this insulating layer is deformed easily by heat, because the insulating layer is usually formed by an organic photoresist insulating layer. Therefore, this insulating layer is deformed by heating treatment at about 250xc2x0 C. during the formation of the thin film coil, and the pattern size of the insulating layer changes, so that the size of throat height TH and MR height might deviate from desired design values.
(4) It is necessary to shorten the throat height TH as much as possible to improve the magnetic property of the inductive type thin film magnetic head and to achieve the small size, but in the conventional combination type thin film magnetic head, a reference position of throat height zero is determined by the position of the edge of the magnetoresistive layer opposite to the air bearing surface, and can not be located at the side of the air bearing surface, therefore, there is a problem that the throat height TH cannot be shortened.
(5) In the reading thin film magnetic head consisting of the magnetoresistive element, it is advantageous to use the GMR element with high sensitivity as a magnetoresistive element, but there is a problem that the reading sensitivity of the GMR element is deteriorated by the heating treatment at about 250xc2x0 C. performed for the photoresist film when the thin film coil of the inductive type thin film magnetic head is formed.
(6) The GMR element of high sensitivity has a structure formed by stacking different kinds of thin films of 1-5 nm thin. Therefore, a lot of manufacturing steps are required for forming the GMR element to complete the combination type thin film magnetic head, so that the electrostatic breakdown occurs during the handling, and thus there is a problem that the manufacturing yield is decreased.
(7) The alumina film having a thickness of 30-40 xcexcm or more is formed as the overcoat layer at the end of the mass production process of the combination type thin film magnetic head for the protection of the device and the stabilization of the quality. Then, the warp might be generated in the substrate, and a lot of particles are generated by the spattering in case of forming the alumina film, so that there is a problem of deterioration in the device characteristic and the generation of defective components. Moreover, as described above, a long time of 15 hours or more is necessary to form a thick alumina film by spattering, therefore, the throughput might be extremely decreased. In addition, there is a problem in that a long time is required for the etching to expose the contact pads of the electrode pattern for the magnetoresistive element.
(8) In the combination type thin film magnetic head, the characteristics of the combination type thin film magnetic head are mainly determined by a width and MR height MRH of the magnetoresistive element of the magnetoresistive type thin film magnetic head, a width of the magnetic pole portion, a throat height TH, and characteristic of NLTS (Non-Linear Transition Shift) for the inductive type thin film magnetic head. Therefore, the requirement of user has concentrated on these specifications. For example, since the width of the magnetoresistive element is decided at an early step of the manufacturing process, when a particular width is specified by a user, a time period until the product is completed, that is, the cycle time becomes very long, and sometimes amounts to 30 to 40 days.
An object of the present invention is to solve or mitigate the various problems of the above conventional combination type thin film magnetic head and to provide a combination type thin film magnetic head which has a minute throat height TH and MR height MRH and has a given apex angle.
Another object of the present invention is to provide a method of manufacturing a combination type thin film magnetic head which has a minute throat height TH and MR height MRH and has a given apex angle, with high yield.
Other object of the present invention is to provide a method of manufacturing a combination type thin film magnetic head capable of reducing a thermal effect for the MR reproduction element, especially the GMR reproduction element.
A further object of the present invention is to provide a method of promptly manufacturing a combination type thin film magnetic head capable of manufacturing the combination type thin film magnetic head having specifications required by user.
According to the present invention, a combination type thin film magnetic head including a magnetoresistive type reading thin film magnetic head having a magnetoresistive element, and an inductive type writing thin film magnetic head in the stacking state, comprises:
a substrate having a recessed portion formed in one major surface;
a first magnetic layer extending along the major surface of the substrate from an end surface defining an air bearing surface to a position near an edge of the recessed portion;
a second magnetic layer extending along a part of an inner surface of the recessed portion such that the said second magnetic layer is magnetically isolated from the first magnetic layer;
a thin film coil at least a part of which is formed within said recessed portion such that the thin film coil is isolated by an insulating layer, said thin film coil constituting the inductive type thin film magnetic head;
a magnetoresistive element arranged in an electrically and magnetically isolated condition within a shield gap layer extending along a plane of the first magnetic layer opposite to the substrate;
a third magnetic layer having a thick portion formed to extend along a plane of said shield gap layer opposite to the substrate and is adjacent to the air bearing surface and a thin portion connected to an edge of the second magnetic layer on the side of the air bearing surface;
an insulating spacer layer formed to bury a step between the thick portion and the thin portion of the third magnetic layer;
a write gap layer extending along at least a plane of the thick portion of the third magnetic layer opposite to the substrate and being separated from the surface of the thin portion of the third magnetic layer opposite to the substrate via said insulating spacer layer; and
a fourth magnetic layer extending along a plane of said write gap layer opposite to the substrate, being opposed to the third magnetic layer, and being magnetically coupled to the second magnetic layer at a rear position apart from the air bearing surface.
According to the present invention, a method of manufacturing a combination type thin film magnetic head having a magnetoresistive type reading thin film magnetic head including a magnetoresistive element, and an inductive type writing thin film magnetic head in the stacking state, comprises the steps of:
forming a recessed portion in a major surface of a substrate;
forming a first magnetic layer extending along the major surface of the substrate from an end surface constituting an air bearing surface to a position near an edge of the recessed portion;
forming a second magnetic layer extending along a part of an inner surface of the recessed portion such that the second magnetic layer is magnetically isolated from the first magnetic layer;
forming a thin film coil constituting the inductive type thin film magnetic head such that at least a part of the thin film coil is formed within the recessed portion to be isolated by an insulating layer;
forming a magnetoresistive element extending along a surface of the first magnetic layer such that the magnetoresistive element is electrically and magnetically isolated;
forming a third magnetic layer extending along a surface of the magnetoresistive element such that the third magnetic layer has a thick portion adjacent to the air bearing surface and a thin portion connected to an edge of the second magnetic layer on the side of the air bearing surface;
forming an insulating spacer layer such that a step between the thick portion and the thin portion of the third magnetic layer is buried and a surface of the insulating spacer layer becomes coplanar with a surface of the thick portion;
forming a flat write gap layer on the coplanar surfaces of the thick portion of the third magnetic layer and the insulating spacer layer;
forming a flat fourth magnetic layer extending along a surface of the write gap layer, being opposed to the thick portion of the third magnetic layer, and being magnetically coupled to the second magnetic layer at a rear position apart from the air bearing surface; and
polishing the air bearing surface.
Moreover, according to the present invention, a method of manufacturing a combination type thin film magnetic head having a magnetoresistive type reading thin film magnetic head including a magnetoresistive element, and an inductive type writing thin film magnetic head in the stacked state, comprises the steps of:
manufacturing and stocking a plurality of common thin film magnetic head units common to combination type thin film magnetic heads having various characteristics, each of said units including a substrate having a recessed portion formed therein, a first magnetic layer extending along a surface of the substrate from an end face constituting an air bearing surface to a position near an edge of the recessed portion, a second magnetic layer extending along a part of an inner surface of the recessed portion such that the second magnetic layer is magnetically isolated from the first magnetic layer, and at least a part of the thin film coil constituting the inductive type thin film magnetic head, said part of the thin film coil being formed in the recessed portion to be isolated by an insulating layer;
wherein the following steps are performed for a common thin film magnetic head unit in accordance with characteristics of a thin film magnetic head to be manufactured;
forming a magnetoresistive element extending along a surface of the first magnetic layer such that the magnetoresistive element is electrically and magnetically isolated;
forming a third magnetic layer extending along a surface of the magnetoresistive element such that the third magnetic layer has a thick portion adjacent to the air bearing surface and a thin portion connected to an edge of the second magnetic layer on the side of the air bearing surface;
forming an insulating spacer layer such that a step between the thick portion and the thin portion of the third magnetic layer is buried by the spacer layer and a surface of the insulating spacer layer becomes coplanar with a surface of the thick portion;
forming a flat write gap layer on the coplanar surfaces of the thick portion of the third magnetic layer and the insulating spacer layer;
forming a flat fourth magnetic layer extending along a surface of the write gap layer, being opposed to the thick portion of the third magnetic layer, and being magnetically coupled to the second magnetic layer at a rear position apart from the air bearing surface; and
polishing the air bearing surface.
In the above mentioned combination type thin film magnetic head according to the present invention, one of the yokes and one of the poles of the inductive type thin film magnetic head are divided into the second magnetic layer formed in the recessed portion and the third magnetic layer formed at the magnetic pole portion, and the third magnetic layer is constituted by the thick portion adjacent to the air bearing side and the thin portion connected with the edge of the second magnetic layer on the air bearing surface side, and thus the step between these two portions is buried with the insulating spacer layer. These points differ greatly from the conventional combination type thin film magnetic head. By adopting such a constitution, the reference position of throat height zero of the inductive type thin film magnetic head is determined by the step formed at the boundary between the different thickness portions constituting the third magnetic layer, and this position of the step can be set independently from the position of the edge of the magnetoresistive layer constituting the magnetoresistive element opposite to the air bearing side. For instance, it is possible to set the step position which is superposed with the magnetic resistance layer, and thus the throat height can be shortened compared with the conventional combination type thin film magnetic head. Moreover, the apex angle is determined by an inclination angle of a side wall of the recessed portion, and it is preferable to set said inclination angle of the side wall of the recessed portion to 45-75xc2x0, especially 55-65xc2x0.
In addition, in the combination type thin film magnetic head according to the present invention, the surface of the thick portion of the third magnetic layer opposite to the substrate is coplanar with the surface of the insulating spacer layer, and therefore the write gap layer as well as the fourth magnetic layer formed thereon can be made flat, and thus the magnetic head having desired size and shape can be easily manufactured. Furthermore, the overcoat layer formed on the fourth magnetic layer can be also flat, so that its thickness can be small and unwanted stress due to the overcoat layer can be reduced.
In addition, in the combination type thin film magnetic head according to the present invention, the third magnetic layer is preferably made of a material whose saturation magnetic flux density is higher than that of the second magnetic layer. As stated above, in the combination type thin film magnetic head according to the present invention, the bottom yoke and bottom pole are divided into two magnetic layers, i.e. the second and third magnetic layers. When the third magnetic layer constituting the magnetic pole is made of a material whose saturation flux density is higher than that of the second magnetic layer, the treatment during the manufacturing process becomes easy and the manufacturing cost can be lowered as compared with the case in which both the yoke and the entire pole is made of a material having a high saturation magnetic flux density.
In addition, according to the manufacturing method of the combination type thin film magnetic head of the present invention, after the thin film coil is formed within the recessed portion, the magnetoresistive element is formed. Therefore, the magnetoresistive element is not exposed to heating treatment for forming the thin film coil, the problem of deterioration in characteristics of the magnetoresistive element does not occur, and thus the reading GMR element with a high sensitivity, but is liable to be affected by heat can be advantageously used.
In the manufacturing method of the combination type thin film magnetic head according to the present invention, it is preferable that said step of forming the recessed portion and said step of forming the first magnetic layer include a step of forming, on the substrate, the first magnetic layer as a mask with an aperture corresponding to the recessed portion, and a step of forming the recessed portion in the surface of the substrate by performing etching while said first magnetic layer is used as a mask. In this case, it is preferable to conduct the formation of the first magnetic layer plating and to perform the formation of the recessed portion by reactive ion etching. Then, the deep recessed portion having a depth not less than 5 xcexcm can be formed accurately.
In addition, in the method of manufacturing a thin film magnetic head, in which a plurality of common thin film magnetic head units commonly usable for manufacturing combination type thin film magnetic heads having various characteristics are previously manufactured and stocked, it is possible to be able to correspond to various demands of users promptly, and thus the cycle time until the product is completed can be remarkably shortened.